CN203232132U - Look-up table based digital photovoltaic array simulation system - Google Patents

Abstract

The utility model provides a digital photovoltaic array simulator system based on a look-up table method, with a step-down chopper circuit (BUCK circuit) with a synchronous rectification method, the BUCK circuit is connected to the input end of a controller through a signal conditioning module, and the controller The output end is connected to the input end of the metal oxide semiconductor field effect transistor (MOSFET) drive module, and the output end of the MOSFET drive module is connected to the BUCK circuit; the power supply module is connected to the signal conditioning module, the controller and the MOSFET drive module, and the load resistor is connected to the signal conditioning module. The system provided by the utility model overcomes the deficiencies of the prior art, can carry out research on photovoltaic power generation systems around the clock, has high energy utilization rate, can replace photovoltaic characteristic curves online, and has the characteristics of large power, small volume and low storage cost.

Description

Digital Photovoltaic Array Simulator System Based on Look-up Table Method

technical field

The utility model relates to a digital photovoltaic array simulator system based on a look-up table method, which belongs to the technical field of photovoltaic power generation.

Background technique

Photovoltaic power generation is one of the main ways to utilize solar energy at present, and it is also a research hotspot. A photovoltaic array is a device that converts solar energy into electrical energy and is an extremely important component of a photovoltaic power generation system. The quality of the photovoltaic array directly affects the power generation of the photovoltaic power generation system.

The working characteristics of photovoltaic arrays are very different under different sunlight and ambient temperatures, that is, their output power presents obvious nonlinear characteristics with parameters such as sunlight intensity and ambient temperature. Taking a photovoltaic cell with an open circuit voltage of 40V, a short circuit current of 3.5A, and a maximum power point of 33V and 3A as an example, its photovoltaic characteristic curve is shown in Figure 1. Therefore, in order to convert the output of photovoltaic array cells into stable and reliable electrical energy, the photovoltaic power generation system must have the "all-weather" ability to adapt to this nonlinearity. However, in the natural environment, conditions such as sunlight intensity and temperature will obviously change at any time due to factors such as time, season, and geographical location. Therefore, if the actual photovoltaic array is used in the experiment, not only the cost is high, but also the experimental results will be inaccurate due to the limitations of the installation location and experimental time, and the experimental equipment cannot reach the required rated power, nor can it meet the "all-weather" continuous Experimental requirements. In order to solve the problem that the photovoltaic array is constrained by natural conditions in the experiment, the concept of photovoltaic array simulator is proposed.

Existing photovoltaic array simulators are mainly divided into analog and digital. The simulated photovoltaic array simulator is mainly based on the sample photovoltaic cell simulator. It uses the imitation sunlight lamp to irradiate the photovoltaic array. The output voltage and current of the sample photovoltaic cell change with the simulated light intensity. The voltage and current are amplified to drive the power device. Its output follows the voltage and current of the sample photovoltaic cell, instead of the actual photovoltaic array for testing. The digital photovoltaic array simulator is mainly a non-linear switching power supply that uses the control of a digital signal processor (DSP) or a single-chip microcomputer to make the output voltage and current meet the photovoltaic characteristic curve.

The energy utilization rate of the existing photovoltaic array simulator is low, and the existing photovoltaic array simulator realizes the change of the photovoltaic characteristic curve by storing multiple curve data. This method requires a large amount of storage space, so that the memory needs to be expanded , increasing storage costs.

Utility model content

The technical problem to be solved by the utility model is to provide a digital photovoltaic array simulator system based on the look-up table method with high energy utilization rate, all-weather photovoltaic power generation system research and low storage cost.

In order to solve the above-mentioned technical problems, the technical solution of the utility model is to provide a digital photovoltaic array simulator system based on the look-up table method, which is characterized in that: a step-down chopper circuit (BUCK circuit) with synchronous rectification, BUCK circuit The signal conditioning module is connected to the input terminal of the controller, the output terminal of the controller is connected to the input terminal of the metal oxide semiconductor field effect transistor (MOSFET) driving module, and the output terminal of the MOSFET driving module is connected to the BUCK circuit; the power supply module is connected to the signal conditioning module, the controller and The MOSFET drive module, and the load resistor is connected to the signal conditioning module.

Preferably, the BUCK circuit with synchronous rectification includes an input power supply, the positive pole of the input power supply is connected to the drain of the first field effect transistor, the negative pole of the input power supply is connected to the source of the second field effect transistor, one end of the filter capacitor and the The signal conditioning module, the source of the first field effect transistor is connected to the drain of the second field effect transistor and one end of the filter inductor, the other end of the filter inductor is connected to the other end of the filter capacitor and the signal conditioning module, the first field effect The gate of the transistor and the gate of the second field effect transistor are both connected to the MOSFET drive module.

Preferably, the signal conditioning module includes a Hall sensor, the first pin of the Hall sensor is connected to one end of the load resistor, and the other end of the load resistor is connected to one end of the second voltage dividing resistor and the negative pole of the input power supply. The other end of the two voltage divider resistors is connected to one end of the first voltage divider resistor and the voltage sampling end of the controller, and the other end of the first voltage divider resistor is connected to the other end of the filter inductor and the third pin of the Hall sensor. The output end of the sensor is connected to the current sampling end of the controller, and the Hall sensor is also connected to the power supply module.

The utility model provides a digital photovoltaic array simulator system based on the table look-up method, which uses an embedded system as the core device, the main circuit adopts a BUCK conversion circuit with synchronous rectification, and the key photovoltaic characteristic curve adopts an offline Computer calculation, that is, import the corresponding discrete voltage and current corresponding values into the controller after calculation on the computer, and input the voltage and current output by the main circuit to the controller after passing through the signal conditioning circuit. The voltage signal corresponds to the look-up table to obtain the corresponding current reference signal, and the error signal between the current reference signal and the sampled current signal is used to control the output, thereby realizing the simulation of the photovoltaic array battery.

Compared with the prior art, the beneficial effects of a digital photovoltaic array simulator system based on the look-up table method provided by the utility model are as follows:

(1) Due to the application of the synchronous rectification method, the energy utilization rate of the system is higher than that of the general simulator, and the research of the photovoltaic power generation system can be carried out around the clock, and the power is relatively large;

(2) Using the method of changing curves online, only need to store the capacity of two curve data, the volume is much smaller than photovoltaic cells, the energy utilization rate is high, the photovoltaic characteristic curve can be replaced online, and the system storage cost is low.

The system provided by the utility model overcomes the deficiencies of the prior art, and can conduct research on photovoltaic power generation systems around the clock, has high energy utilization rate, can replace photovoltaic characteristic curves online, and has the characteristics of large power, small volume and low storage cost.

Description of drawings

Fig. 1 is the schematic diagram of photovoltaic characteristic curve;

Fig. 2 is a system block diagram of a digital photovoltaic array simulator based on the look-up table method provided by the utility model;

Fig. 3 is a circuit schematic diagram of a digital photovoltaic array simulator system based on the look-up table method provided by the utility model.

Detailed ways

In order to make the utility model more obvious and understandable, a preferred embodiment is described in detail as follows in conjunction with the accompanying drawings.

Fig. 2 is a schematic block diagram of a digital photovoltaic array simulator system based on the table look-up method provided by the present invention. The main circuit of the digital photovoltaic array simulator system based on the table look-up method adopts a synchronous The rectified BUCK circuit, the BUCK circuit is connected to the input terminal of the controller through the signal conditioning module, the output terminal of the controller is connected to the input terminal of the MOSFET driver module, and the output terminal of the MOSFET driver module is connected to the BUCK circuit; the power supply module is connected to the signal conditioning module, the controller and the MOSFET driver module, and the load resistor R3 is connected to the signal conditioning module.

Combined with Figure 3, the BUCK circuit with synchronous rectification includes an input power supply E, the positive pole of the input power supply E is connected to the drain of the first field effect transistor Q1, the negative pole of the input power supply E is connected to the source of the second field effect transistor Q2, and the filter capacitor One end of C1 and the signal conditioning module, the source of the first field effect transistor Q1 is connected to the drain of the second field effect transistor Q2 and one end of the filter inductor L1, and the other end of the filter inductor L1 is connected to the other end of the filter capacitor C1 and In the signal conditioning module, the gate of the first field effect transistor Q1 and the gate of the second field effect transistor Q2 are both connected to the MOSFET driving module.

The first FET Q1 and the second FET Q2 are IRF840 produced by IR Company.

After the output from the BUCK circuit, it is connected to the signal conditioning module. The signal conditioning module includes a Hall sensor P1. The first pin of the Hall sensor P1 is connected to one end of the load resistor R3, and the other end of the load resistor R3 is connected to the end of the second voltage dividing resistor R2 and the The negative pole of the input power supply E, the other end of the second voltage dividing resistor R2 is connected to one end of the first voltage dividing resistor R1 and the voltage sampling end of the controller, and the other end of the first voltage dividing resistor R1 is connected to the other end of the filter inductor L1 and the third pin of the Hall sensor P1, the output end of the Hall sensor P1 is connected to the current sampling end of the controller, and the Hall sensor P1 is also connected to the power supply module.

The Hall sensor P1 is ACS712ELCTR-05B produced by Allegro, which can convert the current signal into AD (analog-to-digital conversion) and can accept 0-3.3V. Two voltage-dividing resistors R1 and R2 control the voltage value at 0-3.3V. Then carry out the AD sampling of the output voltage and current.

The controller adopts the TQ2440 development board produced by Tianxie Company, and the concrete model of the microprocessor is the ARM9 processor S3C2440 of Samsung Company. The processor has a total of 8 channels of AD sampling, and the voltage and current sampling terminals of the signal conditioning module are connected to channel 0 and channel 1 respectively. Channel 0 obtains the given current signal by checking the photovoltaic characteristic table. The given current signal and the error signal of channel 1 are connected to the input terminal of the PID regulator, and the output terminal of the PID regulator is connected to the PWM generator. The PWM wave generated by the PWM generator is used as a MOSFET driver. The control signal of the module, which is connected to the MOSFET drive circuit.

The driver chip corresponding to the MOSFET driver module is IR2117 produced by IR Company. The output terminal of the driver module is connected to the BUCK circuit, and the PWM signal transformed by the MOSFET driver module is used to control the switch of the field effect tube for closed-loop adjustment, so that the photovoltaic array simulator The output voltage and current meet the output characteristics of photovoltaic array cells.

The power supply module is preferably an L4978 chip produced by STMicroelectronics, and the power supply module is connected with a controller module, a MOSFET drive module and a signal conditioning module.

In use, the photovoltaic inverter or load resistor R3 is connected to the BUCK circuit. First, calculate the required photovoltaic characteristic curve on an ordinary PC, and the photovoltaic characteristic curve satisfies the following equation:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; sc</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; oc</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="C"\; filenames="HDA00002790391800011.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; sc</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; mp</span>}}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; oc</span>}}<span\; class="notranslate">\; )</span>}$

C ₂ =(V _m /V _oc -1)[ln(1-I _m /I _sc )] ^-1

Among them, I _sc , V _oc , I _m , V _m , I _L , and V _L represent the short-circuit current, open-circuit voltage, current corresponding to the maximum power point, voltage corresponding to the maximum power point, output current, and output voltage respectively. C ₁ , C ₂ is an intermediate process parameter.

Use the method of numerical calculation on the PC to discretize the voltage evenly. According to the above equation, substitute the corresponding technical parameters to obtain the discrete value of the current, and convert the obtained discrete value of voltage and current into 10-bit precision AD correspondence. The integer values of the two groups of AD values are stored in the S3C2440 controller on-chip random access memory (RAM) in order to control the search.

The voltage AD value obtained by sampling is searched for the corresponding voltage AD array stored in RAM, and according to the AD reference value of the current corresponding to the voltage value, the difference between the current AD reference value and the actual AD sampling value is used as the error signal for PID adjustment. The PWM wave is generated as the control signal of the MOSFET drive module. The signal is connected to the MOSFET drive circuit, and the drive voltage is converted to 15V through the IR2117. The converted PWM signal is used to control the switches of the field effect transistors Q1 and Q2 for closed-loop adjustment, so that The voltage and current output by the photovoltaic array simulator meet the output characteristics of photovoltaic array cells. Since the Schottky diode with the smallest tube voltage drop is generally selected for the freewheeling diode, it also has an on-state tube voltage drop of at least 0.6V, and the on-state impedance of the field effect tube is generally about 10 milliohms, so the field effect tube is used instead of the Schottky diode. The base diode can reduce switching losses. To change the photovoltaic characteristic curve, send the new photovoltaic characteristic curve to the RAM of the development board through the serial port, and then replace the photovoltaic curve after it is completely received, so that there is no need to store multiple curve data, and It is to use the method of on-line replacement curve to realize the change of photovoltaic characteristic curve.

The utility model provides a digital photovoltaic array simulator system based on the table look-up method based on the photovoltaic cell model, through the controller and the power electronic conversion device, the photovoltaic power generation system research can be carried out around the clock, and the power is large and the volume It is much smaller than photovoltaic cells, has high energy utilization rate, can replace photovoltaic characteristic curves online, and has low system storage overhead.

Claims (3)

1. digital photovoltaic array simulation system based on look-up table, it is characterized in that: comprise the buck circuit that has synchronous rectification, buck circuit connects the controller input end by the signal condition module, controller output end connects metal oxide semiconductor field effect tube driver module input end, and metal oxide semiconductor field effect tube driver module output terminal connects buck circuit; The power supply module connects signal condition module, controller and metal oxide semiconductor field effect tube driver module, and pull-up resistor (R3) connects the signal condition module.

2. a kind of digital photovoltaic array simulation system based on look-up table as claimed in claim 1, it is characterized in that: the described buck circuit that has synchronous rectification comprises input power supply (E), the positive pole of input power supply (E) connects the drain electrode of first field effect transistor (Q1), the negative pole of input power supply (E) connects the source electrode of second field effect transistor (Q2), one end of filter capacitor (C1) and described signal condition module, the source electrode of first field effect transistor (Q1) connects the drain electrode of second field effect transistor (Q2) and an end of filter inductance (L1), the other end of filter inductance (L1) connects the other end and the described signal condition module of filter capacitor (C1), and the grid of the grid of first field effect transistor (Q1) and second field effect transistor (Q2) all is connected described metal oxide semiconductor field effect tube driver module.

3. a kind of digital photovoltaic array simulation system based on look-up table as claimed in claim 2, it is characterized in that: described signal condition module comprises Hall element (P1), first pin of Hall element (P1) connects described pull-up resistor (R3) end, described pull-up resistor (R3) other end connects the negative pole of second divider resistance (R2) end and described input power supply (E), second divider resistance (R2) other end connects the voltage sample end of first divider resistance (R1) end and described controller, first divider resistance (R1) other end connects the other end of described filter inductance (L1) and the 3rd pin of Hall element (P1), the output terminal of Hall element (P1) connects the current sample end of described controller, and Hall element (P1) also connects described power supply module.

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